I have run the following query over 200 times without an error:
INSERT INTO tempAbsenceClientUpload SELECT FirstName, LastName, UserID, UserIsActive, Email, TopClient, ClientGroup, isUpdated, MainProcessID, rownumber FROM temporaryAbsClientTable
Which simply takes from one table to another.
However, I now get the following error message: Subquery returns more than 1 row Error
Can anyone help me to understand why?
I don't really want alternative code suggestions, just why it happened.
Thanks.
There was an 'on insert' trigger on the destination table. The data being entered was referenced against a third table in an expression expecting a single result (two results were being generated).
So the 'sub routine' was connected to a function in a trigger on the destination table firing due to the insert.
Thanks for everyone's ideas.
You might have duplicates in the second table.
IN that case you could do this to eliminate them:(create a copy of your table first)
ALTER IGNORE TABLE tableName ADD UNIQUE KEY keyName (`columnName`);
OR to check for duplicates:
select columnNameWithDuplicates, count(*) from tableName group by (columnNameWithDuplicates) having count(*)>1;
I think you are missing a WHERE clause which is giving this error
Related
I keep getting the following error when I try to insert a record into a table:
[ColumnName] cannot be modified because it is either a computed column or is the result of a UNION operator.
This column is actually a computed column, but I simply added the table to the EDMX and now it gives this error when I insert. Obviously I am not trying to insert into the computed column, but it still throws this error.
Does anyone know how I can solve this?
I am trying to delete a row from a table but while deleting the entry, MySQL is giving me the following error:
Column count doesn't match value count at row 1.
the query which is i m executing is a simnple delete query:
DELETE from 'tablename' WHERE id=1341
Make sure you don't have any triggers on delete statement.
You can see you triggers by SHOW TRIGGERS;
AND if you want to drop one of the triggers DROP [name_of_the_trigger];
DELETE from tablename WHERE id=1341
(without quotes) i guess is the correct answer
I've been trying to learn SQL using python to update a db and am trying to do something simple. Iterate through a csv file that includes the fortune 500 with their revenue info and push into an SQL db. I've run it a few times and it's working great, the only issue is I'm getting duplicates because I've run the same file a few times.
In the future, I'm assuming it's good to learn how to avoid duplicates. After looking around this is what I've found for a proposed solution using WHERE NOT EXISTS but am getting an error. Any advice is welcome as I'm totally new.
Note - I do know I should be updating more than one row at a time, that's my next lesson
import pymysql
import csv
with open('companies.csv','rU') as f:
reader = csv.DictReader(f)
for i in reader:
conn = pymysql.connect(host='host', user='user', passwd='pw', db='db_test')
cur = conn.cursor()
query1 = "INSERT INTO companies (Name, Revenue, Profit, Stock_Price) VALUES (\'{}\',{},{},{})".format(str(i['Standard']),float(i['Revenues']),float(i['Profits']),float(i['Rank']))
query2 = 'WHERE NOT EXISTS (SELECT Name FROM companies WHERE Name = \'{}\')'.format(str(i['Standard']))
query = query1+' '+query2
cur.execute(query)
conn.commit()
cur.close()
OUTPUT:
INSERT INTO companies (Name, Revenue, Profit, Stock_Price) VALUES ('WalMart Stores',469.2,16999.0,1.0) WHERE NOT EXISTS (SELECT Name FROM companies WHERE Name = 'WalMart Stores')
ERROR:
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'WHERE NOT EXISTS (SELECT Name FROM companies WHERE Name = 'WalMart Stores')' at line 1")
Ok. First of all, congratulations on self-learning!
Now, to the point.
When you use insert ... values, you can't define a where condition for the table on which you're inserting values. insert statement is only used to insert (When you use insert... select, you can define a where condition on the select, not on the table on which you're about to insert values).
So, there are two ways to do what you want:
Create a unique index on the column that you want to test, and then use insert ignore...
In your code, check if the value is already there, and if it's not, then insert it.
I'll tell you how to work with the first suggestion, because it'll teach you a couple of things. As for suggestion 2, I'll leave that for you as homework ;-)
First, you need to add a unique index to your table. If you want to avoid duplicates on the Name column, then:
alter table companies
add unique index idx_dedup_name(Name);
Check the syntax for ALTER TABLE.
And now, let's say that Companies already has a row with name 'XCorp'. If you try a normal INSERT... VALUES statement here, you'll get an error, because you're trying to add a duplicate value. If you want to avoid that error, you can use something like this:
insert ignore into companies(name) values ('XCorp');
This will execute as a normal insert, but, since you're trying to insert a duplicate value, it will fail, but silently (it wil throw a warning instead of an error).
As for suggestion 2, as I told you, I leave it to you as homework.
Hints:
Count the rows where the name matches a value.
Read the count to a variable in your python program
Test the value... if there's zero entries, then perform the insert.
i'm using MySQL and i want to check if a record exists and if it exists delete this record.
i try this but it 's not working for me:
SELECT 'Barcelone' AS City, EXISTS(SELECT 1 FROM mytable WHERE City = 'Barcelone') AS 'exists';
THEN
DELETE FROM mytable
WHERE City = 'Barcelone';
Thank you for your help.
The if statement is only allowed in stored procedures, stored functions, and triggers (in MySQL).
If I understand what you want, just do:
DELETE FROM mytable
WHERE City = 'Barcelone';
There is no reason to check for the existence beforehand. Just delete the row. If none exist, no problem. No errors.
I would recommend an index on mytable(city) for performance reasons. If you want to check if the row exists first, that is fine, but it is unnecessary for the delete.
If you mean MySQL is returning an error message (if that's what you mean by "not working for me"), then that's exactly the behavior we would expect.
That SQL syntax is not valid for MySQL.
If you want to delete rows from a table, issue a DELETE statement, e.g.
DELETE FROM mytable WHERE City = 'Barcelone'
If you want to know how many rows were deleted (if the statement doesn't throw an error), immediately follow the DELETE statement (in the same session) with a query:
SELECT ROW_COUNT()
Or the appropriate function in whatever client library you are using.
If the ROW_COUNT() function returns 0, then there were no rows deleted.
There's really no point (in terms of MySQL) in issuing a SELECT to find out if there are rows to be deleted; the DELETE statement itself will figure it out.
If for some reason your use case requires you to check whether there are rows be be deleted, then just run a separate SELECT:
SELECT COUNT(1) FROM mytable WHERE City = 'Barcelone'
Is there any way to select a record and update it in a single query?
I tried this:
UPDATE arrc_Voucher
SET ActivatedDT = now()
WHERE (SELECT VoucherNbr, VoucherID
FROM arrc_Voucher
WHERE ActivatedDT IS NULL
AND BalanceInit IS NULL
AND TypeFlag = 'V'
LIMIT 1 )
which I hoped would run the select query and grab the first record that matches the where clause, the update the ActivatedDT field in that record, but I got the following error:
1241 - Operand should contain 1 column(s)
Any ideas?
How about:
UPDATE arrc_Voucher
SET ActivatedDT = NOW()
WHERE ActivatedDT IS NULL
AND BalanceInit IS NULL
AND TypeFlag = 'V'
LIMIT 1;
From the MySQL API documentation :
UPDATE returns the number of rows that were actually changed
You cannot select a row and update it at the same time, you will need to perform two queries to achieve it; fetch your record, then update it.
If you are worrying about concurrent processes accessing the same row through some kind of race condition (supposing your use case involve high traffic), you may consider other alternatives such as locking the table (note that other processes will need to recover--retry--if the table is locked while accessing it)
Or if you can create stored procedure, you may want to read this article or the MySQL API documentation.
But about 99% of the time, this is not necessary and the two queries will execute without any problem.